linux-kernel - Re: [PATCH] cxl/pci: replace use of system_wq with system_percpu

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Message-ID: <ce2f5f34-8855-41eb-9f4e-6bdaaaae90b4@intel.com>
Date: Mon, 3 Nov 2025 16:44:14 -0700
From: Dave Jiang <dave.jiang@...el.com>
To: Marco Crivellari <marco.crivellari@...e.com>,
 linux-kernel@...r.kernel.org, linux-cxl@...r.kernel.org
Cc: Tejun Heo <tj@...nel.org>, Lai Jiangshan <jiangshanlai@...il.com>,
 Frederic Weisbecker <frederic@...nel.org>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
 Michal Hocko <mhocko@...e.com>, Davidlohr Bueso <dave@...olabs.net>,
 Jonathan Cameron <jonathan.cameron@...wei.com>,
 Alison Schofield <alison.schofield@...el.com>,
 Vishal Verma <vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>,
 Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH] cxl/pci: replace use of system_wq with system_percpu_wq



On 10/30/25 9:38 AM, Marco Crivellari wrote:
> Currently if a user enqueue a work item using schedule_delayed_work() the
> used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
> WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
> schedule_work() that is using system_wq and queue_work(), that makes use
> again of WORK_CPU_UNBOUND.
> 
> This lack of consistency cannot be addressed without refactoring the API.
> 
> system_wq should be the per-cpu workqueue, yet in this name nothing makes
> that clear, so replace system_wq with system_percpu_wq.
> 
> The old wq (system_wq) will be kept for a few release cycles.
> 
> Suggested-by: Tejun Heo <tj@...nel.org>
> Signed-off-by: Marco Crivellari <marco.crivellari@...e.com>

Applied to cxl/next
952e9057e66c17a9718232664368ffdaca468f93

> ---
>  drivers/cxl/pci.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
> index bd100ac31672..0be4e508affe 100644
> --- a/drivers/cxl/pci.c
> +++ b/drivers/cxl/pci.c
> @@ -136,7 +136,7 @@ static irqreturn_t cxl_pci_mbox_irq(int irq, void *id)
>  	if (opcode == CXL_MBOX_OP_SANITIZE) {
>  		mutex_lock(&cxl_mbox->mbox_mutex);
>  		if (mds->security.sanitize_node)
> -			mod_delayed_work(system_wq, &mds->security.poll_dwork, 0);
> +			mod_delayed_work(system_percpu_wq, &mds->security.poll_dwork, 0);
>  		mutex_unlock(&cxl_mbox->mbox_mutex);
>  	} else {
>  		/* short-circuit the wait in __cxl_pci_mbox_send_cmd() */